Cognitive and Motor Aspects of Parkinson's Disease Associated with Dysphagia

Background: Dysphagia is a common symptom and an important prognostic factor in Parkinson's disease (PD). Although cognitive and motor dysfunctions may contribute to dysphagia in patients with PD, any specific association between such problems and swallowing functions is unclear. Here, we examined the potential relationship between cognitive/motor components and swallowing functions in PD. We evaluated the contributions of cognition and motor function to the components of swallowing via video fluoroscopic swallowing (VFS) experiments. Methods: We prospectively enrolled 56 patients without dementia having PD. Parkinson's disease severity was assessed by the Unified Parkinson's Disease Rating Scale (UPDRS). All participants received neuropsychological tests covering general mental status, visuospatial function, attention, language, learning and memory, and frontal executive function. The well-validated modified barium swallow impairment profile scoring system was applied during VFS studies to quantify swallowing impairments. Finally, correlations between neuropsychological or motor functions and impairment in swallowing components were calculated. Results: The most significant correlations were found between the frontal/executive or learning/memory domains and the oral phase of swallowing, though a minor component of the pharyngeal phase correlated with frontal function as well. Bradykinesia and the UPDRS total score were associated with both the pharyngeal and oral phases. Conclusions: Our findings suggest that cognitive dysfunctions are associated with the oral phase of swallowing in patients with early stage PD while the severity of motor symptoms may be associated with overall swallowing function.